Flame-retardant cellulose triacetate articles

ABSTRACT

A composition and solution for forming shaped articles comprising cellulose acetate, from 1 to 20 percent of a bromoaliphatic phosphate containing from 10 to 30 percent bromine and from 0.4 to 3 percent of a second compound selected from the group consisting of phenyl phosphates, cresyl phosphates, di(tbutyl) peroxide, dicumyl peroxide, and 2,5-dimethyl-2,5-di(tbutyl-5-peroxy) hexane.

United States Patent 1 1 3,615,746

[72] Inventors Willard C. Brinegar [56] References Cited N- UNITEDSTATES PATENTS gggg? Alma 2,574,515 1 1/1951 Walter et a1. 260/956 [21]2,675,327 4/1954 Gearhart 106/176 22 1 Filed Dec. 10, 1969 26 19712,858,228 /1958 Hughes... 106 190 {g} 22:25:: gg Corporation 3,121,1062/1964 Nagy 260/952 New York, N Y FOREIGN PATENTS Continuation-in-partof application Sen No, 821,431 10/1959 Great Britain 106/196 562! July1966 now abandoned Primary Examiner- Lorenzo B. Hayes Attorneys-ThomasJ. Morgan, Stephen D. Murphy and Andrew F. Sayko, Jr.

[54] FLAME-RETARDANT CELLULOSE TRIACETATE :gg ghf Draw. ABSTRACT: Acomposition and solution for forming shaped mgs articles comprisingcellulose acetate, from 1 to percent of a [52] U.S. I 106/15,bromo-aliphatic phosphate containing from 10 to 30 percent 106/177,106/190, 106/196, 251/8.1 bromine and from 0.4 to 3 percent of a secondcompound [51] Int. Cl C08b 21/04 selected from the group consisting ofphenyl phosphates, Field of Search 106/15 FP, cresyl phosphates,di(t-butyl) peroxide, dicumyl peroxide, and

177, 252/8.1; 186/196 2,5-dimethyl-2,5-di(t-butyl-5-peroxy) hexane.

FLAME-RETARDANT CELLULOSE TRIACETATE ARTICLES This invention is acontinuation-in-part of U.S. application Ser. No. 562,1 19 filed July 1,1966 now abandoned.

This invention relates to improved self-extinguishing cellulosetriacetate articles, and a process of producing them.

Cellulose triacetate has found wide commercial acceptance as manmadefibers for textiles, nonwoven products and the like. While theseproducts are for the most part suitable in the end-use applications forwhich they are utilized, there are uses for which increased flameretardance would be very desirable. Such uses are wearing apparel andhousehold furnishings, such as draperies, and upholstery fabrics.

it is an object of this invention to provide shaped articles ofcellulose triacetate having increased flameproofing.

lt is a further object of this invention to provide low-denier fiberproducts of cellulose triacetate which do not support combustion whencontacted with a flame after the flame is removed.

It is a still further object of this invention to impartselfextinguishing properties to shaped articles of cellulose triacetatewithout serious sacrifice of their other favorable properties such asmechanical and dyeing properties.

In accordance with this invention, there is incorporated into an organicsolvent solution of cellulose triacetate a minor amount of abromo-aliphatic phosphate and a minor amount of a second additivecompound selected from the group consisting of phenyl phosphates, cresylphosphates, di(t-butyl) peroxide, dicumyl peroxide and2,5-dirnethyl-2,5-di(t-butyl-5- peroxy) hexane. The contemplated phenyland cresyl phosphates are preferably unsubstituted phosphates havingthree phenyl or three cresyl groups, e.g. triphenyl phosphate,o-phenylphenyl bis-phenyl phosphate, tricresyl phosphate ortris-o-phenylphenyl phosphate.

The organic solvent solutions of cellulose triacetate to which thisinvention may be applied are conventional spinning or casting solutionsfor the production of filaments and films respectively which generallycontain about to 30 percent by weight of cellulose triacetate. Thesolvent used is preferably methylene chloride but other solvents may beused such as ethylene chloride.

THe bromo-aliphatic phosphate may contain open and/or cyclic aliphaticgroups and may be a bromine-substituted alkyl or cycloalkyl phosphate inwhich the substituted alkyl groups contain 3 to 8 carbon atoms. Thebromine content of the bromo-aliphatic phosphate is preferably about 10to 30 percent by weight. Some specific compounds which may be used aretris(2,3-dibromo-propyl) phosphate, which is preferred,tris(2,-bromobutyl) phosphate, tris(bromohexyl) phosphate, and tris(bromocyclohexyl) phosphate.

THe bromo-aliphatic phosphate is used in the solution of cellulosetriacetate in an amount of at least 1 percent, preferably 1 to percent,and most preferably in an amount of S to l0 percent by weight of thecellulose triacetate, whereas the second additive compound is used in anamount of 0.4 to 3 percent, preferably 0.4 to 1 percent based on theweight of cellulose triacetate.

The total amount of additives used is less than the amount ofbromo-aliphatic phosphate or second additive compound which would benecessary to produce an equivalent fire-retardant effect in a shapedarticle (e.g., fiber or film) of cellulose triacetate, when used alone.

As is well known in the art, cellulose triacetate is a cellulose acetatecontaining at least 59 percent preferably at least 61 percent by weightof acetyl group calculated as combined acetic acid. Thus, cellulosetriacetate may be distinguished from secondary cellulose acetate whichgenerally contains about 54 to 56 percent of acetyl groups calculated ascombined acetic acid.

In addition to the flameproofing agents of this invention, the organicsolvent solution of cellulose triacetate may contain other modifyingcomponents, e.g., pigments for dulling or coloring the yarn or film,plasticizers, stabilizers, etc.

The following examples further illustrate the invention:

EXAMPLE I In a spinning solution of 20 weight percent of cellulosetriacetate having an acetyl value of about 61.5 percent calculated ascombined acetic acid in a solvent composed of 9l percent methylenechloride and 9 percent methanol were dissolved 5 percent based on theweight of cellulose triacetate of tris(2,3-dibromopropyl) phosphate and1 percent based on the weight of cellulose triacetate of o-phenyl-phenylbisphenyl phosphate. This modified spinning solution was extruded in adownward direction through a spinnerette containing 40 holes each 36microns in diameter into a spinning column of 7 inches in diameter and 7feet long containing air traveling in an upward direction. Thetemperature of the spinnerette face was C. and the average airtemperature in the spinning column was 50 C. The takeup speed of theresulting yarn was meters per minute.

Tl-le resulting cellulose triacetate yarn had a total denier of 143, atendency of 1.33 grams per denier, an elongation of 24.0 percent and wasself-extinguishing when subjected to the flame test described below.

EXAMPLE I! THe procedure of example I was repeated except that tricresylphosphate was used in place of O-phenylphenyl bisphenyl phosphate in anamount of 1 percent based on the weight of the cellulose triacetate.

The resulting yarn had a total denier of 75, a tenacity of 1.10 gramsper denier, an elongation of 27.5 percent and was self-extinguishingwhen subjected to the flame test described below.

EXAMPLE Ill The procedure of example 1 was repeated except that theophenylphenyl bisphenyl phosphate was replaced by 1 percent based on theweight of cellulose triacetate of di-t-butyl peroxide.

The resulting yarn had a total denier of 160, a tenacity ofgrams/denier, an elongation of 26.2 was self-extinguishing using theflame test described below.

EXAMPLES IV and V The procedure of example 1 is repeated except that theophenylphenyl bisphenyl phosphate is replaced by 1 percent based on theweight of cellulose triacetate of dicumyl peroxide (example 1V) and2,5-dimethyl-2,5-di(t-butyl-5-peroxy) hexane (example V).

Satisfactory self-extinguishing yarns are obtained which areself-extinguishing when subjected to the flame test described below. Theflame test of the yarn products described in examples I to V was carriedout as follows:

The yarn was knitted into a hose leg, a 6 to 8 inch section of which wassuspended vertically from a support placed in an area essentially freefrom direct air drafts. The freely hanging lower edge of the fabric wasignited with a luminous flame from either a Bunsen burner or a papersafety match. After the initial ignition of the fabric, the flame wasremoved and the burning characteristics of the fabric were observed. Thesample was considered to be self-extinguishing if the flame wasrepeatedly extinguished after several ignitions of the same fabricsample.

Although the foregoing disclosure of the invention primarily describedfibers as shaped articles, the compositions of the invention may also beused to form flame-retardant films and molded articles. Thus, theorganic solvent solution of cellulose triacetate and additives may becast into films or precipitated to form flake which may subsequently beinjectionor compression-molded. Y

EXAMPLE Vl In a casting solution of 10 weight percent of cellulosetriacetate having an acetyl value of about 6l .5 percent calculated ascombined acetic acid in a solvent composed of 91 per- EXAMPLES VII,VIII, IX, X and XI The procedure of example VI was repeated except thatthe following additives were added to the casting solution in place of 1percent tris(2,3-dibromopropyl) phosphate and 0.2 percent o-phenylphenylbisphenyl phosphate:

Additives to CTA solution in methylene chloride/methanol Example VII 2%tris(2,3-dibromopropyl) phosphate Example VIII l% tris(2,3dibromopropyl) phosphate and 0.4% o-phenyl phenyl bisphenyl phosphateExample IX l% tris(2,3-dibrm0propyl) phosphate and 0.4%tris-ophenylphenyl phosphate Example X tris(2,3-dibromopr0pyl) phosphateand 0.4% tricresyl phosphate Example Xl ltris(Z,3-dibromopropyl)phosphate and 0.4% triphenyl phosphate The film of example VII burnedwhen subjected to the flame test described below. The films of examplesVIII, IX, X and XI were self-extinguishing when subjected to the flametest described below.

The flame test for the films described in examples VII to Xl was carriedout as follows:

The film was cut into three 3 inch by 6 inch strips held rigid in ametal U-frame. The rigid strips were held vertically and ignited with aBunsen burner. After the initial ignition of the film, the flame wasremoved and the burning characteristics of the film were observed. Thesample was considered to be selfextinguishing if the flame wasrepeatedly extinguished after several ignitions of the same film sample.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of our invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A composition comprising cellulose triacetate having an acetyl valueof at least 59 percent by weight calculated as combined acetic acid, anda flame-retardant amount of a synergistic flame-retardant mixturecomprising from 1 percent to 20 percent by weight based on the weight ofthe cellulose triacetate of a bromo-aliphatic phosphate containing about10 percent to 30 percent by weight of bromine, said bromoaliphaticphosphate selected from the group consisting of bromine-substitutedalkyl and cycloalkyl phosphates wherein said alkyl group contains from 3to 8 carbon atoms and from 0.4 percent to 3 by weight based on theweight of the cellulose triacetate of a second additive compoundselected from the group consisting of phenyl phosphates, cresylphosphates, di(t-butyl) peroxide, dicumyl peroxide, and2,5-dimethyl-2,5- di(t-butyl-S-peroxy) hexane.

2. The composition of claim 1 in the form ofa shaped article.

3. The product of claim 2 wherein said shaped article is a fiber.

4. The product of claim 2 wherein said shaped article is a film.

5. The product of claim 1 wherein said bromo-aliphatic compound is tris(Z3-dibromopropyl) phosphate and said second additive compound iso-phenylphenyl bisphenyl phosphate.

6. The product of claim 1 wherein said bromo-aliphatic phosphate istris(2,3-dibromopropyl) phosphate and said second additive compound istricresyl phosphate.

7. The composition of claim 1 containing from 5 to 10 percent by weightof said bromo-aliphatic phosphate and from 0.4 to 1 percent by weight ofsaid second additive compound.

8. A solution of cellulose triacetate having an acetyl value of at least59 percent calculated as combined acetic acid suitable for forming intoshaped articles containing from 1 percent to 20 percent by weight basedon the weight of cellulose triacetate of bromo-aliphatic phosphatecontaining about 10 to 30 percent by weight of bromine, saidbromo-aliphatic phosphate selected from the group consisting ofbromine-substituted alkyl and cycloalkyl phosphates wherein said alkylgroup contains from 3 to 8 carbon atoms and from 0.4 to 1 percent byweight based on the weight of cellulose triacetate of a second additivecompound selected from the group consisting of phenyl phosphates, cresylphosphates, di(t-butyl) peroxide, dicumyl peroxide, and2,5-dimethyl-2.5-di(t-butyl- 5-peroxy) hexane.

9. The solution of claim 8 wherein the solvent is principally composedof methylene chloride, said bromo-aliphatic phosphate istris(2,3-dibromopropyl) phosphate and said second additive compound is aphenyl phosphate.

10. Tile solution of claim 8 wherein the solvent is principally composedof methylene chloride, said bromo-aliphatic phosphate istris(2,3-dibromopropyl) phosphate and said second additive compound is acresyl phosphate.

11. The composition of claim 8 containing from 5 to 10 percent by weightof said bromo-aliphatic phosphate and from 0.4 to 1 percent by weight ofsaid second additive compound.

12. A process for forming a shaped article comprising dissolving in asolvent cellulose triacetate having an acetyl value of at least 59 byweight calculated as combined acetic acid, from I to 20 percent byweight based on the weight of cellulose triacetate oftris(2,3-dibromopropyl) phosphate and from 0.4 to 1 percent by weightbased on the weight of cellulose triacetate of a second additivecompound selected from the group consisting of phenyl phosphates, cresylphosphates, di(t-butyl) peroxide, dicumyl peroxide, and2,5-dimethyl-2,5- di(t-butyl-S-peroxy) hexane.

13. The process of claim 12 wherein said solvent is principally composedof methylene chloride, said second additive compound is o-phenylphenylbisphenyl phosphate, and said shaped article is a filament.

14. The process of claim 12 wherein said solvent is principally composedof methylene chloride, said second additive compound is tricresylphosphate, and said shaped article is a filament.

15. The process ofclaim 12 wherein from 5 to 10 percent by weight ofsaid phosphate is dissolved in said solvent.

16. A film comprising cellulose triacetate having an acetyl value of atleast 59 percent by weight calculated as combined acetic acid, and aflame-retardant amount of a synergistic flame retardant mixturecomprising from l to 20 percent by weight based on the weight of thecellulose triacetate of a bromo-aliphatic phosphate containing about 10to 30 percent by weight of bromine, said bromo-aliphatic phosphateselected from the group consisting of bromine-substituted alkyl andcycloalkyl phosphates wherein said alkyl group contains from 3 to 8carbon atoms and from 0.2 to 3 percent by weight based on the weight ofcellulose triacetate of a second additive compound selected from thegroup consisting of phenyl phosphates, cresyl phosphates, di(t-butyl)peroxide, dicumyl peroxide, and 2,5-dimethyl2,5-di(t-butyl-5 -peroxy)hexane.

UNITED STATES PATENT OFFECE Patent 6151.745 Dawd Sci-r1259): rm, 1 m

Inventm-(s) Willard C. Brinegar, Jcseph iiiPietro It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby ccrrectec'i as shown below:

Column 3 e X, e" shouii be Calumn 3, Example X1, 1" should be ----l%--Column 3 65,

Calumn claim 3.2, "59 slwuld ha ----59 percent Signed and sealed this23rd day of May 1932.

, line 19, "tenfieznc?" should be ---tenacity--- claim 1, "3" should be--3 percent--- Attest:

2311mm: R. ROBERT GOTHSCRQLK attesting 051 new Commissioner 0f Patents

2. The composition of claim 1 in the form of a shaped article.
 3. Theproduct of claim 2 wherein said shaped article is a fiber.
 4. Theproduct of claim 2 wherein said shaped article is a film.
 5. The productof claim 1 wherein said bromo-aliphatic compound istris(2,3-dibromopropyl) phosphate and said second additive compound iso-phenylphenyl bisphenyl phosphate.
 6. The product of claim 1 whereinsaid bromo-aliphatic phosphate is tris(2,3-dibromopropyl) phosphate andsaid second additive compound is tricresyl phosphate.
 7. The compositionof claim 1 containing from 5 to 10 percent by weight of saidbromo-aliphatic phosphate and from 0.4 to 1 percent by weight of saidsecond additive compound.
 8. A solution of cellulose triacetate havingan acetyl value of at least 59 percent calculated as combined aceticacid suitable for forming into shaped articles containing from 1 percentto 20 percent by weight based on the weight of cellulose triacetate of abromo-aliphatic phosphate containing about 10 to 30 percent by weight ofbromine, said bromo-aliphatic phosphate selected from the groupconsisting of bromine-substituted alkyl and cycloalkyl phosphateswherein said alkyl group contains from 3 to 8 carbon atoms and from 0.4to 1 percent by weight based on the weight of cellulose triacetate of asecond additive compound selected from the group consisting of phenylphosphates, cresyl phosphates, di(t-butyl) peroxide, dicumyl peroxide,and 2,5-dimethyl-2,5-di(t-butyl-5-peroxy) hexane.
 9. The solution ofclaim 8 wherein the solvent is principally composed of methylenechloride, said bromo-aliphatic phosphate is tris(2,3-dibromopropyl)phosphate and said second additive compound is a phenyl phosphate. 10.The solution of claim 8 wherein the solvent is principally composed ofmethylene chloride, said bromo-aliphatic phosphate istris(2,3-dibromopropyl) phosphate and said second additive compound is acresyl phosphate.
 11. The composition of claim 8 containing from 5 to 10percent by weight of said bromo-aliphatic phosphate and from 0.4 to 1percent by weight of said second additive compound.
 12. A process forforming a shaped article comprising dissolving in a solvent cellulosetriacetate having an acetyl value of at least 59 percent by weightcalculated as combined acetic acid, from 1 to 20 percent by weight basedon the weight of cellulose triacetate of tris(2,3-dibromopropyl)phosphate and from 0.4 to 1 percent by weight based on the weight ofcellulose triacetate of a second additive compound selected from thegroup consisting of phenyl phosphates, cresyl phosphates, di(t-butyl)peroxide, dicumyl peroxide, and 2,5-dimethyl-2,5-di(t-butyl-5-peroxy)hexane.
 13. The process of claim 12 wherein said solvent is principallycomposed of methylene chloride, said second additive compound iso-phenylphenyl bisphenyl phosphate, and said shaped article is afilament.
 14. The process of claim 12 wherein said solvent isprincipally composed of methylene chloride, said second additivecompound is tricresyl phosphate, and saId shaped article is a filament.15. The process of claim 12 wherein from 5 to 10 percent by weight ofsaid phosphate is dissolved in said solvent.
 16. A film comprisingcellulose triacetate having an acetyl value of at least 59 percent byweight calculated as combined acetic acid, and a flame-retardant amountof a synergistic flame retardant mixture comprising from 1 to 20 percentby weight based on the weight of the cellulose triacetate of abromo-aliphatic phosphate containing about 10 to 30 percent by weight ofbromine, said bromo-aliphatic phosphate selected from the groupconsisting of bromine-substituted alkyl and cycloalkyl phosphateswherein said alkyl group contains from 3 to 8 carbon atoms and from 0.2to 3 percent by weight based on the weight of cellulose triacetate of asecond additive compound selected from the group consisting of phenylphosphates, cresyl phosphates, di(t-butyl) peroxide, dicumyl peroxide,and 2,5-dimethyl-2,5-di(t-butyl-5 -peroxy) hexane.